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Summary: The options aren't supported so they can be removed. Reviewers: beanz, smeenai, compnerd Reviewed By: compnerd Subscribers: mgorny, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D69877
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1132 lines
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ReStructuredText
====================================
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Getting Started with the LLVM System
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====================================
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.. contents::
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:local:
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Overview
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========
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Welcome to the LLVM project!
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The LLVM project has multiple components. The core of the project is
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itself called "LLVM". This contains all of the tools, libraries, and header
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files needed to process intermediate representations and converts it into
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object files. Tools include an assembler, disassembler, bitcode analyzer, and
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bitcode optimizer. It also contains basic regression tests.
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C-like languages use the `Clang <http://clang.llvm.org/>`_ front end. This
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component compiles C, C++, Objective C, and Objective C++ code into LLVM bitcode
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-- and from there into object files, using LLVM.
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Other components include:
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the `libc++ C++ standard library <https://libcxx.llvm.org>`_,
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the `LLD linker <https://lld.llvm.org>`_, and more.
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Getting the Source Code and Building LLVM
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=========================================
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The LLVM Getting Started documentation may be out of date. The `Clang
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Getting Started <http://clang.llvm.org/get_started.html>`_ page might have more
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accurate information.
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This is an example workflow and configuration to get and build the LLVM source:
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#. Checkout LLVM (including related subprojects like Clang):
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* ``git clone https://github.com/llvm/llvm-project.git``
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* Or, on windows, ``git clone --config core.autocrlf=false
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https://github.com/llvm/llvm-project.git``
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#. Configure and build LLVM and Clang:.
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* ``cd llvm-project``
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* ``mkdir build``
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* ``cd build``
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* ``cmake -G <generator> [options] ../llvm``
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Some common generators are:
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* ``Ninja`` --- for generating `Ninja <https://ninja-build.org>`_
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build files. Most llvm developers use Ninja.
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* ``Unix Makefiles`` --- for generating make-compatible parallel makefiles.
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* ``Visual Studio`` --- for generating Visual Studio projects and
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solutions.
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* ``Xcode`` --- for generating Xcode projects.
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Some Common options:
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* ``-DLLVM_ENABLE_PROJECTS='...'`` --- semicolon-separated list of the LLVM
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subprojects you'd like to additionally build. Can include any of: clang,
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clang-tools-extra, libcxx, libcxxabi, libunwind, lldb, compiler-rt, lld,
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polly, or debuginfo-tests.
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For example, to build LLVM, Clang, libcxx, and libcxxabi, use
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``-DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi"``.
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* ``-DCMAKE_INSTALL_PREFIX=directory`` --- Specify for *directory* the full
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pathname of where you want the LLVM tools and libraries to be installed
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(default ``/usr/local``).
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* ``-DCMAKE_BUILD_TYPE=type`` --- Valid options for *type* are Debug,
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Release, RelWithDebInfo, and MinSizeRel. Default is Debug.
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* ``-DLLVM_ENABLE_ASSERTIONS=On`` --- Compile with assertion checks enabled
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(default is Yes for Debug builds, No for all other build types).
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* Run your build tool of choice!
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* The default target (i.e. ``ninja`` or ``make``) will build all of LLVM.
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* The ``check-all`` target (i.e. ``ninja check-all``) will run the
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regression tests to ensure everything is in working order.
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* CMake will generate build targets for each tool and library, and most
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LLVM sub-projects generate their own ``check-<project>`` target.
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* Running a serial build will be *slow*. To improve speed, try running a
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parallel build. That's done by default in Ninja; for ``make``, use
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``make -j NNN`` (NNN is the number of parallel jobs, use e.g. number of
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CPUs you have.)
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* For more information see `CMake <CMake.html>`__
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* If you get an "internal compiler error (ICE)" or test failures, see
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`below`_.
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Consult the `Getting Started with LLVM`_ section for detailed information on
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configuring and compiling LLVM. Go to `Directory Layout`_ to learn about the
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layout of the source code tree.
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Requirements
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============
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Before you begin to use the LLVM system, review the requirements given below.
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This may save you some trouble by knowing ahead of time what hardware and
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software you will need.
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Hardware
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--------
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LLVM is known to work on the following host platforms:
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================== ===================== =============
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OS Arch Compilers
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================== ===================== =============
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Linux x86\ :sup:`1` GCC, Clang
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Linux amd64 GCC, Clang
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Linux ARM GCC, Clang
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Linux Mips GCC, Clang
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Linux PowerPC GCC, Clang
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Solaris V9 (Ultrasparc) GCC
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FreeBSD x86\ :sup:`1` GCC, Clang
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FreeBSD amd64 GCC, Clang
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NetBSD x86\ :sup:`1` GCC, Clang
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NetBSD amd64 GCC, Clang
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macOS\ :sup:`2` PowerPC GCC
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macOS x86 GCC, Clang
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Cygwin/Win32 x86\ :sup:`1, 3` GCC
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Windows x86\ :sup:`1` Visual Studio
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Windows x64 x86-64 Visual Studio
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================== ===================== =============
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.. note::
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#. Code generation supported for Pentium processors and up
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#. Code generation supported for 32-bit ABI only
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#. To use LLVM modules on Win32-based system, you may configure LLVM
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with ``-DBUILD_SHARED_LIBS=On``.
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Note that Debug builds require a lot of time and disk space. An LLVM-only build
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will need about 1-3 GB of space. A full build of LLVM and Clang will need around
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15-20 GB of disk space. The exact space requirements will vary by system. (It
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is so large because of all the debugging information and the fact that the
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libraries are statically linked into multiple tools).
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If you are space-constrained, you can build only selected tools or only
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selected targets. The Release build requires considerably less space.
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The LLVM suite *may* compile on other platforms, but it is not guaranteed to do
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so. If compilation is successful, the LLVM utilities should be able to
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assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation
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should work as well, although the generated native code may not work on your
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platform.
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Software
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--------
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Compiling LLVM requires that you have several software packages installed. The
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table below lists those required packages. The Package column is the usual name
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for the software package that LLVM depends on. The Version column provides
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"known to work" versions of the package. The Notes column describes how LLVM
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uses the package and provides other details.
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=========================================================== ============ ==========================================
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Package Version Notes
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=========================================================== ============ ==========================================
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`CMake <http://cmake.org/>`__ >=3.4.3 Makefile/workspace generator
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`GCC <http://gcc.gnu.org/>`_ >=5.1.0 C/C++ compiler\ :sup:`1`
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`python <http://www.python.org/>`_ >=2.7 Automated test suite\ :sup:`2`
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`zlib <http://zlib.net>`_ >=1.2.3.4 Compression library\ :sup:`3`
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`GNU Make <http://savannah.gnu.org/projects/make>`_ 3.79, 3.79.1 Makefile/build processor\ :sup:`4`
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=========================================================== ============ ==========================================
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.. note::
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#. Only the C and C++ languages are needed so there's no need to build the
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other languages for LLVM's purposes. See `below` for specific version
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info.
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#. Only needed if you want to run the automated test suite in the
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``llvm/test`` directory.
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#. Optional, adds compression / uncompression capabilities to selected LLVM
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tools.
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#. Optional, you can use any other build tool supported by CMake.
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Additionally, your compilation host is expected to have the usual plethora of
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Unix utilities. Specifically:
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* **ar** --- archive library builder
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* **bzip2** --- bzip2 command for distribution generation
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* **bunzip2** --- bunzip2 command for distribution checking
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* **chmod** --- change permissions on a file
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* **cat** --- output concatenation utility
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* **cp** --- copy files
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* **date** --- print the current date/time
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* **echo** --- print to standard output
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* **egrep** --- extended regular expression search utility
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* **find** --- find files/dirs in a file system
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* **grep** --- regular expression search utility
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* **gzip** --- gzip command for distribution generation
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* **gunzip** --- gunzip command for distribution checking
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* **install** --- install directories/files
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* **mkdir** --- create a directory
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* **mv** --- move (rename) files
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* **ranlib** --- symbol table builder for archive libraries
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* **rm** --- remove (delete) files and directories
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* **sed** --- stream editor for transforming output
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* **sh** --- Bourne shell for make build scripts
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* **tar** --- tape archive for distribution generation
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* **test** --- test things in file system
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* **unzip** --- unzip command for distribution checking
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* **zip** --- zip command for distribution generation
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.. _below:
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.. _check here:
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Host C++ Toolchain, both Compiler and Standard Library
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------------------------------------------------------
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LLVM is very demanding of the host C++ compiler, and as such tends to expose
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bugs in the compiler. We also attempt to follow improvements and developments in
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the C++ language and library reasonably closely. As such, we require a modern
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host C++ toolchain, both compiler and standard library, in order to build LLVM.
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LLVM is written using the subset of C++ documented in :doc:`coding
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standards<CodingStandards>`. To enforce this language version, we check the most
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popular host toolchains for specific minimum versions in our build systems:
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* Clang 3.5
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* Apple Clang 6.0
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* GCC 5.1
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* Visual Studio 2017
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Anything older than these toolchains *may* work, but will require forcing the
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build system with a special option and is not really a supported host platform.
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Also note that older versions of these compilers have often crashed or
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miscompiled LLVM.
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For less widely used host toolchains such as ICC or xlC, be aware that a very
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recent version may be required to support all of the C++ features used in LLVM.
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We track certain versions of software that are *known* to fail when used as
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part of the host toolchain. These even include linkers at times.
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**GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
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warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
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defined in a discarded section. You can safely ignore these messages as they are
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erroneous and the linkage is correct. These messages disappear using ld 2.17.
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**GNU binutils 2.17**: Binutils 2.17 contains `a bug
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<http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
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times (minutes instead of seconds) when building LLVM. We recommend upgrading
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to a newer version (2.17.50.0.4 or later).
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**GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
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<http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
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intermittent failures when building LLVM with position independent code. The
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symptom is an error about cyclic dependencies. We recommend upgrading to a
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newer version of Gold.
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Getting a Modern Host C++ Toolchain
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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This section mostly applies to Linux and older BSDs. On macOS, you should
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have a sufficiently modern Xcode, or you will likely need to upgrade until you
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do. Windows does not have a "system compiler", so you must install either Visual
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Studio 2017 or a recent version of mingw64. FreeBSD 10.0 and newer have a modern
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Clang as the system compiler.
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However, some Linux distributions and some other or older BSDs sometimes have
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extremely old versions of GCC. These steps attempt to help you upgrade you
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compiler even on such a system. However, if at all possible, we encourage you
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to use a recent version of a distribution with a modern system compiler that
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meets these requirements. Note that it is tempting to install a prior
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version of Clang and libc++ to be the host compiler, however libc++ was not
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well tested or set up to build on Linux until relatively recently. As
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a consequence, this guide suggests just using libstdc++ and a modern GCC as the
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initial host in a bootstrap, and then using Clang (and potentially libc++).
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The first step is to get a recent GCC toolchain installed. The most common
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distribution on which users have struggled with the version requirements is
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Ubuntu Precise, 12.04 LTS. For this distribution, one easy option is to install
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the `toolchain testing PPA`_ and use it to install a modern GCC. There is
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a really nice discussions of this on the `ask ubuntu stack exchange`_ and a
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`github gist`_ with updated commands. However, not all users can use PPAs and
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there are many other distributions, so it may be necessary (or just useful, if
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you're here you *are* doing compiler development after all) to build and install
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GCC from source. It is also quite easy to do these days.
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.. _toolchain testing PPA:
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https://launchpad.net/~ubuntu-toolchain-r/+archive/test
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.. _ask ubuntu stack exchange:
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https://askubuntu.com/questions/466651/how-do-i-use-the-latest-gcc-on-ubuntu/581497#58149
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.. _github gist:
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https://gist.github.com/application2000/73fd6f4bf1be6600a2cf9f56315a2d91
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Easy steps for installing GCC 5.1.0:
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.. code-block:: console
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% gcc_version=5.1.0
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% wget https://ftp.gnu.org/gnu/gcc/gcc-${gcc_version}/gcc-${gcc_version}.tar.bz2
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% wget https://ftp.gnu.org/gnu/gcc/gcc-${gcc_version}/gcc-${gcc_version}.tar.bz2.sig
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% wget https://ftp.gnu.org/gnu/gnu-keyring.gpg
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% signature_invalid=`gpg --verify --no-default-keyring --keyring ./gnu-keyring.gpg gcc-${gcc_version}.tar.bz2.sig`
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% if [ $signature_invalid ]; then echo "Invalid signature" ; exit 1 ; fi
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% tar -xvjf gcc-${gcc_version}.tar.bz2
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% cd gcc-${gcc_version}
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% ./contrib/download_prerequisites
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% cd ..
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% mkdir gcc-${gcc_version}-build
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% cd gcc-${gcc_version}-build
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% $PWD/../gcc-${gcc_version}/configure --prefix=$HOME/toolchains --enable-languages=c,c++
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% make -j$(nproc)
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% make install
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For more details, check out the excellent `GCC wiki entry`_, where I got most
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of this information from.
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.. _GCC wiki entry:
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https://gcc.gnu.org/wiki/InstallingGCC
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Once you have a GCC toolchain, configure your build of LLVM to use the new
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toolchain for your host compiler and C++ standard library. Because the new
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version of libstdc++ is not on the system library search path, you need to pass
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extra linker flags so that it can be found at link time (``-L``) and at runtime
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(``-rpath``). If you are using CMake, this invocation should produce working
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binaries:
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.. code-block:: console
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% mkdir build
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% cd build
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% CC=$HOME/toolchains/bin/gcc CXX=$HOME/toolchains/bin/g++ \
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cmake .. -DCMAKE_CXX_LINK_FLAGS="-Wl,-rpath,$HOME/toolchains/lib64 -L$HOME/toolchains/lib64"
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If you fail to set rpath, most LLVM binaries will fail on startup with a message
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from the loader similar to ``libstdc++.so.6: version `GLIBCXX_3.4.20' not
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found``. This means you need to tweak the -rpath linker flag.
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When you build Clang, you will need to give *it* access to modern C++
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standard library in order to use it as your new host in part of a bootstrap.
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There are two easy ways to do this, either build (and install) libc++ along
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with Clang and then use it with the ``-stdlib=libc++`` compile and link flag,
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or install Clang into the same prefix (``$HOME/toolchains`` above) as GCC.
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Clang will look within its own prefix for libstdc++ and use it if found. You
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can also add an explicit prefix for Clang to look in for a GCC toolchain with
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the ``--gcc-toolchain=/opt/my/gcc/prefix`` flag, passing it to both compile and
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link commands when using your just-built-Clang to bootstrap.
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.. _Getting Started with LLVM:
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Getting Started with LLVM
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=========================
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The remainder of this guide is meant to get you up and running with LLVM and to
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give you some basic information about the LLVM environment.
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The later sections of this guide describe the `general layout`_ of the LLVM
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source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
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more information about LLVM or to get help via e-mail.
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Terminology and Notation
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------------------------
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Throughout this manual, the following names are used to denote paths specific to
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the local system and working environment. *These are not environment variables
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you need to set but just strings used in the rest of this document below*. In
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any of the examples below, simply replace each of these names with the
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appropriate pathname on your local system. All these paths are absolute:
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``SRC_ROOT``
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This is the top level directory of the LLVM source tree.
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``OBJ_ROOT``
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This is the top level directory of the LLVM object tree (i.e. the tree where
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object files and compiled programs will be placed. It can be the same as
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SRC_ROOT).
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Unpacking the LLVM Archives
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---------------------------
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If you have the LLVM distribution, you will need to unpack it before you can
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begin to compile it. LLVM is distributed as a number of different
|
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subprojects. Each one has its own download which is a TAR archive that is
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compressed with the gzip program.
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The files are as follows, with *x.y* marking the version number:
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``llvm-x.y.tar.gz``
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Source release for the LLVM libraries and tools.
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``cfe-x.y.tar.gz``
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Source release for the Clang frontend.
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.. _checkout:
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Checkout LLVM from Git
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----------------------
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You can also checkout the source code for LLVM from Git. While the LLVM
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project's official source-code repository is Subversion, we are in the process
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of migrating to git. We currently recommend that all developers use Git for
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day-to-day development.
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.. note::
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Passing ``--config core.autocrlf=false`` should not be required in
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the future after we adjust the .gitattribute settings correctly, but
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is required for Windows users at the time of this writing.
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Simply run:
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.. code-block:: console
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% git clone https://github.com/llvm/llvm-project.git
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or on Windows,
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.. code-block:: console
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% git clone --config core.autocrlf=false https://github.com/llvm/llvm-project.git
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This will create an '``llvm-project``' directory in the current directory and
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fully populate it with all of the source code, test directories, and local
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copies of documentation files for LLVM and all the related subprojects. Note
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that unlike the tarballs, which contain each subproject in a separate file, the
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git repository contains all of the projects together.
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If you want to get a specific release (as opposed to the most recent revision),
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you can check out a tag after cloning the repository. E.g., `git checkout
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llvmorg-6.0.1` inside the ``llvm-project`` directory created by the above
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command. Use `git tag -l` to list all of them.
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Sending patches
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^^^^^^^^^^^^^^^
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Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
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We don't currently accept github pull requests, so you'll need to send patches
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either via emailing to llvm-commits, or, preferably, via :ref:`Phabricator
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<phabricator-reviews>`.
|
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You'll generally want to make sure your branch has a single commit,
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corresponding to the review you wish to send, up-to-date with the upstream
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``origin/master`` branch, and doesn't contain merges. Once you have that, you
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can use ``git show`` or ``git format-patch`` to output the diff, and attach it
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to a Phabricator review (or to an email message).
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However, using the "Arcanist" tool is often easier. After `installing
|
|
arcanist`_, you can upload the latest commit using:
|
|
|
|
.. code-block:: console
|
|
|
|
% arc diff HEAD~1
|
|
|
|
Additionally, before sending a patch for review, please also try to ensure it's
|
|
formatted properly. We use ``clang-format`` for this, which has git integration
|
|
through the ``git-clang-format`` script. On some systems, it may already be
|
|
installed (or be installable via your package manager). If so, you can simply
|
|
run it -- the following command will format only the code changed in the most
|
|
recent commit:
|
|
|
|
.. code-block:: console
|
|
|
|
% git clang-format HEAD~1
|
|
|
|
Note that this modifies the files, but doesn't commit them -- you'll likely want
|
|
to run
|
|
|
|
.. code-block:: console
|
|
|
|
% git commit --amend -a
|
|
|
|
in order to update the last commit with all pending changes.
|
|
|
|
.. note::
|
|
If you don't already have ``clang-format`` or ``git clang-format`` installed
|
|
on your system, the ``clang-format`` binary will be built alongside clang, and
|
|
the git integration can be run from
|
|
``clang/tools/clang-format/git-clang-format``.
|
|
|
|
|
|
.. _commit_from_git:
|
|
|
|
For developers to commit changes from Git
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
A helper script is provided in ``llvm/utils/git-svn/git-llvm``. After you add it
|
|
to your path, you can push committed changes upstream with ``git llvm
|
|
push``. While this creates a Subversion checkout and patches it under the hood,
|
|
it does not require you to have interaction with it.
|
|
|
|
.. code-block:: console
|
|
|
|
% export PATH=$PATH:$TOP_LEVEL_DIR/llvm-project/llvm/utils/git-svn/
|
|
% git llvm push
|
|
|
|
Within a couple minutes after pushing to subversion, the svn commit will have
|
|
been converted back to a Git commit, and made its way into the official Git
|
|
repository. At that point, ``git pull`` should get back the changes as they were
|
|
committed.
|
|
|
|
You'll likely want to ``git pull --rebase`` to get the official git commit
|
|
downloaded back to your repository. The SVN revision numbers of each commit can
|
|
be found at the end of the commit message, e.g. ``llvm-svn: 350914``.
|
|
|
|
You may also find the ``-n`` flag useful, like ``git llvm push -n``. This runs
|
|
through all the steps of committing _without_ actually doing the commit, and
|
|
tell you what it would have done. That can be useful if you're unsure whether
|
|
the right thing will happen.
|
|
|
|
Reverting a change when using Git
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
If you're using Git and need to revert a patch, Git needs to be supplied a
|
|
commit hash, not an svn revision. To make things easier, you can use
|
|
``git llvm revert`` to revert with either an SVN revision or a Git hash instead.
|
|
|
|
Additionally, you can first run with ``git llvm revert -n`` to print which Git
|
|
commands will run, without doing anything.
|
|
|
|
Running ``git llvm revert`` will only revert things in your local repository. To
|
|
push the revert upstream, you still need to run ``git llvm push`` as described
|
|
earlier.
|
|
|
|
.. code-block:: console
|
|
|
|
% git llvm revert rNNNNNN # Revert by SVN id
|
|
% git llvm revert abcdef123456 # Revert by Git commit hash
|
|
% git llvm revert -n rNNNNNN # Print the commands without doing anything
|
|
|
|
Checkout via SVN (deprecated)
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Until we have fully migrated to Git, you may also get a fresh copy of
|
|
the code from the official Subversion repository.
|
|
|
|
* ``cd where-you-want-llvm-to-live``
|
|
* Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
|
|
* Read-Write: ``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
|
|
|
|
This will create an '``llvm``' directory in the current directory and fully
|
|
populate it with the LLVM source code, Makefiles, test directories, and local
|
|
copies of documentation files.
|
|
|
|
If you want to get a specific release (as opposed to the most recent revision),
|
|
you can check it out from the '``tags``' directory (instead of '``trunk``'). The
|
|
following releases are located in the following subdirectories of the '``tags``'
|
|
directory:
|
|
|
|
* Release 3.5.0 and later: **RELEASE_350/final** and so on
|
|
* Release 2.9 through 3.4: **RELEASE_29/final** and so on
|
|
* Release 1.1 through 2.8: **RELEASE_11** and so on
|
|
* Release 1.0: **RELEASE_1**
|
|
|
|
Local LLVM Configuration
|
|
------------------------
|
|
|
|
Once checked out repository, the LLVM suite source code must be configured
|
|
before being built. This process uses CMake. Unlinke the normal ``configure``
|
|
script, CMake generates the build files in whatever format you request as well
|
|
as various ``*.inc`` files, and ``llvm/include/Config/config.h``.
|
|
|
|
Variables are passed to ``cmake`` on the command line using the format
|
|
``-D<variable name>=<value>``. The following variables are some common options
|
|
used by people developing LLVM.
|
|
|
|
+-------------------------+----------------------------------------------------+
|
|
| Variable | Purpose |
|
|
+=========================+====================================================+
|
|
| CMAKE_C_COMPILER | Tells ``cmake`` which C compiler to use. By |
|
|
| | default, this will be /usr/bin/cc. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| CMAKE_CXX_COMPILER | Tells ``cmake`` which C++ compiler to use. By |
|
|
| | default, this will be /usr/bin/c++. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| CMAKE_BUILD_TYPE | Tells ``cmake`` what type of build you are trying |
|
|
| | to generate files for. Valid options are Debug, |
|
|
| | Release, RelWithDebInfo, and MinSizeRel. Default |
|
|
| | is Debug. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| CMAKE_INSTALL_PREFIX | Specifies the install directory to target when |
|
|
| | running the install action of the build files. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| PYTHON_EXECUTABLE | Forces CMake to use a specific Python version by |
|
|
| | passing a path to a Python interpreter. By default |
|
|
| | the Python version of the interpreter in your PATH |
|
|
| | is used. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| LLVM_TARGETS_TO_BUILD | A semicolon delimited list controlling which |
|
|
| | targets will be built and linked into llvm. |
|
|
| | The default list is defined as |
|
|
| | ``LLVM_ALL_TARGETS``, and can be set to include |
|
|
| | out-of-tree targets. The default value includes: |
|
|
| | ``AArch64, AMDGPU, ARM, BPF, Hexagon, Mips, |
|
|
| | MSP430, NVPTX, PowerPC, Sparc, SystemZ, X86, |
|
|
| | XCore``. |
|
|
| | |
|
|
+-------------------------+----------------------------------------------------+
|
|
| LLVM_ENABLE_DOXYGEN | Build doxygen-based documentation from the source |
|
|
| | code This is disabled by default because it is |
|
|
| | slow and generates a lot of output. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| LLVM_ENABLE_PROJECTS | A semicolon-delimited list selecting which of the |
|
|
| | other LLVM subprojects to additionally build. (Only|
|
|
| | effective when using a side-by-side project layout |
|
|
| | e.g. via git). The default list is empty. Can |
|
|
| | include: clang, libcxx, libcxxabi, libunwind, lldb,|
|
|
| | compiler-rt, lld, polly, or debuginfo-tests. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| LLVM_ENABLE_SPHINX | Build sphinx-based documentation from the source |
|
|
| | code. This is disabled by default because it is |
|
|
| | slow and generates a lot of output. Sphinx version |
|
|
| | 1.5 or later recommended. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| LLVM_BUILD_LLVM_DYLIB | Generate libLLVM.so. This library contains a |
|
|
| | default set of LLVM components that can be |
|
|
| | overridden with ``LLVM_DYLIB_COMPONENTS``. The |
|
|
| | default contains most of LLVM and is defined in |
|
|
| | ``tools/llvm-shlib/CMakelists.txt``. This option is|
|
|
| | not avialable on Windows. |
|
|
+-------------------------+----------------------------------------------------+
|
|
| LLVM_OPTIMIZED_TABLEGEN | Builds a release tablegen that gets used during |
|
|
| | the LLVM build. This can dramatically speed up |
|
|
| | debug builds. |
|
|
+-------------------------+----------------------------------------------------+
|
|
|
|
To configure LLVM, follow these steps:
|
|
|
|
#. Change directory into the object root directory:
|
|
|
|
.. code-block:: console
|
|
|
|
% cd OBJ_ROOT
|
|
|
|
#. Run the ``cmake``:
|
|
|
|
.. code-block:: console
|
|
|
|
% cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=/install/path
|
|
[other options] SRC_ROOT
|
|
|
|
Compiling the LLVM Suite Source Code
|
|
------------------------------------
|
|
|
|
Unlike with autotools, with CMake your build type is defined at configuration.
|
|
If you want to change your build type, you can re-run cmake with the following
|
|
invocation:
|
|
|
|
.. code-block:: console
|
|
|
|
% cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=type SRC_ROOT
|
|
|
|
Between runs, CMake preserves the values set for all options. CMake has the
|
|
following build types defined:
|
|
|
|
Debug
|
|
|
|
These builds are the default. The build system will compile the tools and
|
|
libraries unoptimized, with debugging information, and asserts enabled.
|
|
|
|
Release
|
|
|
|
For these builds, the build system will compile the tools and libraries
|
|
with optimizations enabled and not generate debug info. CMakes default
|
|
optimization level is -O3. This can be configured by setting the
|
|
``CMAKE_CXX_FLAGS_RELEASE`` variable on the CMake command line.
|
|
|
|
RelWithDebInfo
|
|
|
|
These builds are useful when debugging. They generate optimized binaries with
|
|
debug information. CMakes default optimization level is -O2. This can be
|
|
configured by setting the ``CMAKE_CXX_FLAGS_RELWITHDEBINFO`` variable on the
|
|
CMake command line.
|
|
|
|
Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
|
|
directory and issuing the following command:
|
|
|
|
.. code-block:: console
|
|
|
|
% make
|
|
|
|
If the build fails, please `check here`_ to see if you are using a version of
|
|
GCC that is known not to compile LLVM.
|
|
|
|
If you have multiple processors in your machine, you may wish to use some of the
|
|
parallel build options provided by GNU Make. For example, you could use the
|
|
command:
|
|
|
|
.. code-block:: console
|
|
|
|
% make -j2
|
|
|
|
There are several special targets which are useful when working with the LLVM
|
|
source code:
|
|
|
|
``make clean``
|
|
|
|
Removes all files generated by the build. This includes object files,
|
|
generated C/C++ files, libraries, and executables.
|
|
|
|
``make install``
|
|
|
|
Installs LLVM header files, libraries, tools, and documentation in a hierarchy
|
|
under ``$PREFIX``, specified with ``CMAKE_INSTALL_PREFIX``, which
|
|
defaults to ``/usr/local``.
|
|
|
|
``make docs-llvm-html``
|
|
|
|
If configured with ``-DLLVM_ENABLE_SPHINX=On``, this will generate a directory
|
|
at ``OBJ_ROOT/docs/html`` which contains the HTML formatted documentation.
|
|
|
|
Cross-Compiling LLVM
|
|
--------------------
|
|
|
|
It is possible to cross-compile LLVM itself. That is, you can create LLVM
|
|
executables and libraries to be hosted on a platform different from the platform
|
|
where they are built (a Canadian Cross build). To generate build files for
|
|
cross-compiling CMake provides a variable ``CMAKE_TOOLCHAIN_FILE`` which can
|
|
define compiler flags and variables used during the CMake test operations.
|
|
|
|
The result of such a build is executables that are not runnable on the build
|
|
host but can be executed on the target. As an example the following CMake
|
|
invocation can generate build files targeting iOS. This will work on macOS
|
|
with the latest Xcode:
|
|
|
|
.. code-block:: console
|
|
|
|
% cmake -G "Ninja" -DCMAKE_OSX_ARCHITECTURES="armv7;armv7s;arm64"
|
|
-DCMAKE_TOOLCHAIN_FILE=<PATH_TO_LLVM>/cmake/platforms/iOS.cmake
|
|
-DCMAKE_BUILD_TYPE=Release -DLLVM_BUILD_RUNTIME=Off -DLLVM_INCLUDE_TESTS=Off
|
|
-DLLVM_INCLUDE_EXAMPLES=Off -DLLVM_ENABLE_BACKTRACES=Off [options]
|
|
<PATH_TO_LLVM>
|
|
|
|
Note: There are some additional flags that need to be passed when building for
|
|
iOS due to limitations in the iOS SDK.
|
|
|
|
Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general
|
|
<http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information
|
|
about cross-compiling.
|
|
|
|
The Location of LLVM Object Files
|
|
---------------------------------
|
|
|
|
The LLVM build system is capable of sharing a single LLVM source tree among
|
|
several LLVM builds. Hence, it is possible to build LLVM for several different
|
|
platforms or configurations using the same source tree.
|
|
|
|
* Change directory to where the LLVM object files should live:
|
|
|
|
.. code-block:: console
|
|
|
|
% cd OBJ_ROOT
|
|
|
|
* Run ``cmake``:
|
|
|
|
.. code-block:: console
|
|
|
|
% cmake -G "Unix Makefiles" SRC_ROOT
|
|
|
|
The LLVM build will create a structure underneath *OBJ_ROOT* that matches the
|
|
LLVM source tree. At each level where source files are present in the source
|
|
tree there will be a corresponding ``CMakeFiles`` directory in the *OBJ_ROOT*.
|
|
Underneath that directory there is another directory with a name ending in
|
|
``.dir`` under which you'll find object files for each source.
|
|
|
|
For example:
|
|
|
|
.. code-block:: console
|
|
|
|
% cd llvm_build_dir
|
|
% find lib/Support/ -name APFloat*
|
|
lib/Support/CMakeFiles/LLVMSupport.dir/APFloat.cpp.o
|
|
|
|
Optional Configuration Items
|
|
----------------------------
|
|
|
|
If you're running on a Linux system that supports the `binfmt_misc
|
|
<http://en.wikipedia.org/wiki/binfmt_misc>`_
|
|
module, and you have root access on the system, you can set your system up to
|
|
execute LLVM bitcode files directly. To do this, use commands like this (the
|
|
first command may not be required if you are already using the module):
|
|
|
|
.. code-block:: console
|
|
|
|
% mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
|
|
% echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
|
|
% chmod u+x hello.bc (if needed)
|
|
% ./hello.bc
|
|
|
|
This allows you to execute LLVM bitcode files directly. On Debian, you can also
|
|
use this command instead of the 'echo' command above:
|
|
|
|
.. code-block:: console
|
|
|
|
% sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
|
|
|
|
.. _Program Layout:
|
|
.. _general layout:
|
|
|
|
Directory Layout
|
|
================
|
|
|
|
One useful source of information about the LLVM source base is the LLVM `doxygen
|
|
<http://www.doxygen.org/>`_ documentation available at
|
|
`<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
|
|
layout:
|
|
|
|
``llvm/examples``
|
|
-----------------
|
|
|
|
Simple examples using the LLVM IR and JIT.
|
|
|
|
``llvm/include``
|
|
----------------
|
|
|
|
Public header files exported from the LLVM library. The three main subdirectories:
|
|
|
|
``llvm/include/llvm``
|
|
|
|
All LLVM-specific header files, and subdirectories for different portions of
|
|
LLVM: ``Analysis``, ``CodeGen``, ``Target``, ``Transforms``, etc...
|
|
|
|
``llvm/include/llvm/Support``
|
|
|
|
Generic support libraries provided with LLVM but not necessarily specific to
|
|
LLVM. For example, some C++ STL utilities and a Command Line option processing
|
|
library store header files here.
|
|
|
|
``llvm/include/llvm/Config``
|
|
|
|
Header files configured by ``cmake``. They wrap "standard" UNIX and
|
|
C header files. Source code can include these header files which
|
|
automatically take care of the conditional #includes that ``cmake``
|
|
generates.
|
|
|
|
``llvm/lib``
|
|
------------
|
|
|
|
Most source files are here. By putting code in libraries, LLVM makes it easy to
|
|
share code among the `tools`_.
|
|
|
|
``llvm/lib/IR/``
|
|
|
|
Core LLVM source files that implement core classes like Instruction and
|
|
BasicBlock.
|
|
|
|
``llvm/lib/AsmParser/``
|
|
|
|
Source code for the LLVM assembly language parser library.
|
|
|
|
``llvm/lib/Bitcode/``
|
|
|
|
Code for reading and writing bitcode.
|
|
|
|
``llvm/lib/Analysis/``
|
|
|
|
A variety of program analyses, such as Call Graphs, Induction Variables,
|
|
Natural Loop Identification, etc.
|
|
|
|
``llvm/lib/Transforms/``
|
|
|
|
IR-to-IR program transformations, such as Aggressive Dead Code Elimination,
|
|
Sparse Conditional Constant Propagation, Inlining, Loop Invariant Code Motion,
|
|
Dead Global Elimination, and many others.
|
|
|
|
``llvm/lib/Target/``
|
|
|
|
Files describing target architectures for code generation. For example,
|
|
``llvm/lib/Target/X86`` holds the X86 machine description.
|
|
|
|
``llvm/lib/CodeGen/``
|
|
|
|
The major parts of the code generator: Instruction Selector, Instruction
|
|
Scheduling, and Register Allocation.
|
|
|
|
``llvm/lib/MC/``
|
|
|
|
(FIXME: T.B.D.) ....?
|
|
|
|
``llvm/lib/ExecutionEngine/``
|
|
|
|
Libraries for directly executing bitcode at runtime in interpreted and
|
|
JIT-compiled scenarios.
|
|
|
|
``llvm/lib/Support/``
|
|
|
|
Source code that corresponding to the header files in ``llvm/include/ADT/``
|
|
and ``llvm/include/Support/``.
|
|
|
|
``llvm/projects``
|
|
-----------------
|
|
|
|
Projects not strictly part of LLVM but shipped with LLVM. This is also the
|
|
directory for creating your own LLVM-based projects which leverage the LLVM
|
|
build system.
|
|
|
|
``llvm/test``
|
|
-------------
|
|
|
|
Feature and regression tests and other sanity checks on LLVM infrastructure. These
|
|
are intended to run quickly and cover a lot of territory without being exhaustive.
|
|
|
|
``test-suite``
|
|
--------------
|
|
|
|
A comprehensive correctness, performance, and benchmarking test suite
|
|
for LLVM. This comes in a ``separate git repository
|
|
<https://github.com/llvm/llvm-test-suite>``, because it contains a
|
|
large amount of third-party code under a variety of licenses. For
|
|
details see the :doc:`Testing Guide <TestingGuide>` document.
|
|
|
|
.. _tools:
|
|
|
|
``llvm/tools``
|
|
--------------
|
|
|
|
Executables built out of the libraries
|
|
above, which form the main part of the user interface. You can always get help
|
|
for a tool by typing ``tool_name -help``. The following is a brief introduction
|
|
to the most important tools. More detailed information is in
|
|
the `Command Guide <CommandGuide/index.html>`_.
|
|
|
|
``bugpoint``
|
|
|
|
``bugpoint`` is used to debug optimization passes or code generation backends
|
|
by narrowing down the given test case to the minimum number of passes and/or
|
|
instructions that still cause a problem, whether it is a crash or
|
|
miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
|
|
``bugpoint``.
|
|
|
|
``llvm-ar``
|
|
|
|
The archiver produces an archive containing the given LLVM bitcode files,
|
|
optionally with an index for faster lookup.
|
|
|
|
``llvm-as``
|
|
|
|
The assembler transforms the human readable LLVM assembly to LLVM bitcode.
|
|
|
|
``llvm-dis``
|
|
|
|
The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
|
|
|
|
``llvm-link``
|
|
|
|
``llvm-link``, not surprisingly, links multiple LLVM modules into a single
|
|
program.
|
|
|
|
``lli``
|
|
|
|
``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
|
|
(although very slowly...). For architectures that support it (currently x86,
|
|
Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
|
|
compiler (if the functionality was compiled in), and will execute the code
|
|
*much* faster than the interpreter.
|
|
|
|
``llc``
|
|
|
|
``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
|
|
native code assembly file.
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|
|
|
``opt``
|
|
|
|
``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
|
|
(which are specified on the command line), and outputs the resultant
|
|
bitcode. '``opt -help``' is a good way to get a list of the
|
|
program transformations available in LLVM.
|
|
|
|
``opt`` can also run a specific analysis on an input LLVM bitcode
|
|
file and print the results. Primarily useful for debugging
|
|
analyses, or familiarizing yourself with what an analysis does.
|
|
|
|
``llvm/utils``
|
|
--------------
|
|
|
|
Utilities for working with LLVM source code; some are part of the build process
|
|
because they are code generators for parts of the infrastructure.
|
|
|
|
|
|
``codegen-diff``
|
|
|
|
``codegen-diff`` finds differences between code that LLC
|
|
generates and code that LLI generates. This is useful if you are
|
|
debugging one of them, assuming that the other generates correct output. For
|
|
the full user manual, run ```perldoc codegen-diff'``.
|
|
|
|
``emacs/``
|
|
|
|
Emacs and XEmacs syntax highlighting for LLVM assembly files and TableGen
|
|
description files. See the ``README`` for information on using them.
|
|
|
|
``getsrcs.sh``
|
|
|
|
Finds and outputs all non-generated source files,
|
|
useful if one wishes to do a lot of development across directories
|
|
and does not want to find each file. One way to use it is to run,
|
|
for example: ``xemacs `utils/getsources.sh``` from the top of the LLVM source
|
|
tree.
|
|
|
|
``llvmgrep``
|
|
|
|
Performs an ``egrep -H -n`` on each source file in LLVM and
|
|
passes to it a regular expression provided on ``llvmgrep``'s command
|
|
line. This is an efficient way of searching the source base for a
|
|
particular regular expression.
|
|
|
|
``TableGen/``
|
|
|
|
Contains the tool used to generate register
|
|
descriptions, instruction set descriptions, and even assemblers from common
|
|
TableGen description files.
|
|
|
|
``vim/``
|
|
|
|
vim syntax-highlighting for LLVM assembly files
|
|
and TableGen description files. See the ``README`` for how to use them.
|
|
|
|
.. _simple example:
|
|
|
|
An Example Using the LLVM Tool Chain
|
|
====================================
|
|
|
|
This section gives an example of using LLVM with the Clang front end.
|
|
|
|
Example with clang
|
|
------------------
|
|
|
|
#. First, create a simple C file, name it 'hello.c':
|
|
|
|
.. code-block:: c
|
|
|
|
#include <stdio.h>
|
|
|
|
int main() {
|
|
printf("hello world\n");
|
|
return 0;
|
|
}
|
|
|
|
#. Next, compile the C file into a native executable:
|
|
|
|
.. code-block:: console
|
|
|
|
% clang hello.c -o hello
|
|
|
|
.. note::
|
|
|
|
Clang works just like GCC by default. The standard -S and -c arguments
|
|
work as usual (producing a native .s or .o file, respectively).
|
|
|
|
#. Next, compile the C file into an LLVM bitcode file:
|
|
|
|
.. code-block:: console
|
|
|
|
% clang -O3 -emit-llvm hello.c -c -o hello.bc
|
|
|
|
The -emit-llvm option can be used with the -S or -c options to emit an LLVM
|
|
``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
|
|
the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
|
|
|
|
#. Run the program in both forms. To run the program, use:
|
|
|
|
.. code-block:: console
|
|
|
|
% ./hello
|
|
|
|
and
|
|
|
|
.. code-block:: console
|
|
|
|
% lli hello.bc
|
|
|
|
The second examples shows how to invoke the LLVM JIT, :doc:`lli
|
|
<CommandGuide/lli>`.
|
|
|
|
#. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
|
|
|
|
.. code-block:: console
|
|
|
|
% llvm-dis < hello.bc | less
|
|
|
|
#. Compile the program to native assembly using the LLC code generator:
|
|
|
|
.. code-block:: console
|
|
|
|
% llc hello.bc -o hello.s
|
|
|
|
#. Assemble the native assembly language file into a program:
|
|
|
|
.. code-block:: console
|
|
|
|
% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
|
|
|
|
% gcc hello.s -o hello.native # On others
|
|
|
|
#. Execute the native code program:
|
|
|
|
.. code-block:: console
|
|
|
|
% ./hello.native
|
|
|
|
Note that using clang to compile directly to native code (i.e. when the
|
|
``-emit-llvm`` option is not present) does steps 6/7/8 for you.
|
|
|
|
Common Problems
|
|
===============
|
|
|
|
If you are having problems building or using LLVM, or if you have any other
|
|
general questions about LLVM, please consult the `Frequently Asked
|
|
Questions <FAQ.html>`_ page.
|
|
|
|
.. _links:
|
|
|
|
Links
|
|
=====
|
|
|
|
This document is just an **introduction** on how to use LLVM to do some simple
|
|
things... there are many more interesting and complicated things that you can do
|
|
that aren't documented here (but we'll gladly accept a patch if you want to
|
|
write something up!). For more information about LLVM, check out:
|
|
|
|
* `LLVM Homepage <http://llvm.org/>`_
|
|
* `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
|
|
* `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_
|
|
|
|
.. _installing arcanist: https://secure.phabricator.com/book/phabricator/article/arcanist_quick_start/
|